As is known in the art, there are a variety of techniques for addressing motion of objects in radar return signals. One known method to address an unknown motion problem is to use an MIT (moving target indicator) radar dwell to obtain an estimate of target range rate, which can be used on a subsequent radar imaging dwell to compensate for target linear motion. However, with this technique, the range rate information can become stale between the MTI dwell and imaging dwell, and any non-uniform motion may not be handled by the fixed range rate parameter from MTI.
It is also possible to estimate the target range rate from its Doppler location within the range-Doppler map. This location translates to a range rate, however, it is possible that the target could be aliased in Doppler. Unwrapping the aliases may be possible by checking for range-walk. Using the range-Doppler map solves the latency problem associated with using an MTI dwell, but may not allow for time-dependent motion compensation over the imaging Coherent Processing Interval (CPI).
Another known method attempts to estimate target acceleration. However, motion models may not be realistic, especially over longer CPIs. For maritime targets, data-driven techniques for motion compensation have been used. These techniques look for phase changes between successive pulses to estimate an instantaneous range rate. This measurement tends to be noisy, so smoothing filters are implemented to reduce noise. However, causal smoothing filters have the effect of introducing a time lag between the motion estimate and truth, where the size of the lag depends on the filter gain. Also, these methods do not have to address competing ground clutter. Maritime targets generally have a sufficiently large RCS (radar cross section) that the ship scatterers dominate the motion compensation solution over the background sea clutter. However, such methods may not work for smaller land targets that are competing with much larger ground clutter.